Engine speed controller of work machine

Abstract

The present invention is to reduce the flow rate of pressure oil discharged from a main pump and returned to a tank when specific work is executed with an operation amount of an operating device being made small in the state in which an engine is kept at an idling speed. According to the present invention, there is provided a main controller (20) which is capable of controlling the speed of an engine (11) to a normal work speed at which a work implement such as a boom (4) can perform normal work and which controls the speed of the engine (11) to an idling speed serving as a speed lower than the normal work speed when an operating device has returned from an operating position to a neutral position. Configuration is made such that the main controller (20) performs a control process for bringing the speed of the engine (11) to a specific work speed serving as a speed higher than the idling speed but lower than the normal work speed, on detecting execution of the specific work which is performed with an operation amount of the operating device such as a boom operating device (16) being kept small in a state in which the speed of the engine (11) is kept at the idling speed.

Claims

1. An engine speed controller of a working machine, the engine speed controller being provided in the working machine, the working machine having an engine (11), a main pump (12) driven by the engine (11), a hydraulic cylinder (7, 8) operating due to pressure oil discharged from the main pump (12) to thereby drive a work implement (4, 5), a directional control valve (14, 15) controlling the flow of the pressure oil supplied from the main pump (12) to the hydraulic cylinder (7, 8), and an operating device (16, 17) performing switching operation on the directional control valve (14, 15), the engine speed controller comprising: a main controller (20) which is capable of controlling the speed of the engine (11) to a normal work speed at which the work implement (4, 5) can perform normal work and which controls the speed of the engine (11) to an idling speed serving as a speed lower than the normal work speed when the operating device (16, 17) has been returned from an operating position to a neutral position, wherein: the main controller (20) performs a control process for bringing the speed of the engine (11) to a specific work speed which is higher than the idling speed but lower than the normal work speed, on detecting execution of the specific work which is performed with an operation amount of the operating device (16, 17) being kept small in the state in which the speed of the engine (11) is kept at the idling speed.

2. An engine speed controller of a working machine according to claim 1, wherein: the main controller (20) detects the execution of the specific work based on at least one of the operation amount of the operating device (16, 17), an operation speed of the operating device (16, 17), and pump discharge pressure serving as discharge pressure of the main pump (12).

3. An engine speed controller of a working machine according to claim 2, wherein: the main controller (20) performs a control process for bringing the engine speed to the normal work speed on detecting execution of the normal work when the control process for bringing the engine speed to the specific work speed is being performed due to the detection of the execution of the specific work.

4. An engine speed controller of a working machine according to claim 3, wherein: the main controller (20) performs a control process to increase the engine speed gradually from the specific work speed up to the normal work speed.

5. An engine speed controller of a working machine according to claim 1, wherein: the main controller (20) performs a control process for bringing the engine speed to the normal work speed on detecting execution of the normal work when the control process for bringing the engine speed to the specific work speed is being performed due to the detection of the execution of the specific work.

6. An engine speed controller of a working machine according to claim 5, wherein: the main controller (20) performs a control process to increase the engine speed gradually from the specific work speed up to the normal work speed.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 A side view showing a hydraulic excavator taken as an example of a working machine.

(2) FIG. 2 An electric and hydraulic circuit diagram showing an engine speed controller according to an embodiment of the present invention provided in the hydraulic excavator shown in FIG. 1.

(3) FIG. 3 A view showing the configuration of a main part of amain controller provided in the engine speed controller according to the embodiment of the present invention shown in FIG. 2.

(4) FIG. 4 A view showing the configurations of three function setting portions included in the main controller shown in FIG. 3.

(5) FIG. 5 A view showing the configuration of a main part of amain controller provided in another embodiment of the present invention.

(6) FIG. 6 A flow chart showing a processing procedure in the main controller shown in FIG. 5.

DESCRIPTION OF EMBODIMENTS

(7) Embodiments of an engine speed controller of a working machine according to the present invention will be described below in accordance with the drawings.

(8) FIG. 1 is a side view showing a hydraulic excavator taken as an example of the working machine.

(9) As shown in FIG. 1, the hydraulic excavator is provided with a travelling body 1, a swinging body 2 which is disposed on the travelling body 1, and a front working device 3 which is attached to the swinging body 2 so as to be rotatable in an up/down direction. The front working device 3 is provided with a boom 4 which is attached to the swinging body 2, an arm 5 which is attached to a distal end of the boom 4, and a bucket 6 which is attached to a distal end of the arm 5. Each of the boom 4, the arm 5 and the bucket 6 constitutes a work implement. In addition, the front working device 3 is also provided with hydraulic cylinders such as a boom cylinder 7 which drives the boom 4, an arm cylinder 8 which drives the arm 5, and a bucket cylinder 9 which drives the bucket 6.

(10) FIG. 2 is an electric and hydraulic circuit diagram showing an engine speed controller according to an embodiment of the present invention provided in the hydraulic excavator shown in FIG. 1.

(11) The electric and hydraulic circuit shown in FIG. 2 shows a main part of the engine speed controller according to the embodiment of the present invention, from which the bucket cylinder 9 etc. has been removed.

(12) As shown in FIG. 2, the engine speed controller according to the embodiment is provided with an engine 11, a main pump 12 which is driven by the engine 11, and a pilot pump 13. In addition, in the embodiment, there are provided the boom cylinder 7 which drives the aforementioned boom 4, the arm cylinder 8 which drives the arm 5, directional control valves such as a boom directional control valve 14 and an arm directional control valve 15 which control the flow of pressure oil supplied from the main pump 12 to the boom cylinder 7 and the arm cylinder 8 respectively, and operating devices such as a boom operating device 16 and an arm operating device 17 which perform switching operation on the boom directional control valve 14 and the arm directional control valve 15 respectively.

(13) Further, in the embodiment, there is provided a main controller 20 which is capable of controlling the speed of the engine 11 to a normal work speed at which a work implement such as the boom 4 or the arm 5 can perform normal work, and which controls the speed of the engine 11 to an idling speed serving as a speed lower than the normal work speed when an operating device such as the boom operating device 16 etc. has been returned from an operating position to a neutral position. Moreover, particularly, the main controller 20 provided in the embodiment performs a control process for bringing the speed of the engine 11 to a specific work speed serving as a speed which is higher than the idling speed but lower than the normal work speed, on detecting execution of specific work such as light load work which is performed with an operation amount of the operating device being kept small in the state in which the speed of the engine 11 is kept at the idling speed.

(14) FIG. 3 is a view showing the configuration of a main part of the main controller provided in the engine speed controller according to the embodiment of the present invention shown in FIG. 2. FIG. 4 is a view showing the configurations of three function setting portions included in the main controller shown in FIG. 3.

(15) The main controller 20 detects the execution of the aforementioned specific work based on at least one of the operation amount of the operating device, an operation speed of the operating device, and pump discharge pressure serving as discharge pressure of the main pump 12. For example, in the embodiment, configuration is made such that the execution of the specific work is detected based on all the three detection factors, i.e. the operation amount of the operating device, the operation speed of the operating device, and the pump discharge pressure.

(16) As shown in FIGS. 2 and 3, in the embodiment, there are provided a pressure sensor 18 which detects the operation amount of the operating device such as the boom operating device 16 or the arm operating device 17, a calculation portion 20c which is included in the main controller 20 and which calculates the operation speed of the operating device based on a signal outputted from the pressure sensor 18, and a discharge pressure sensor 19 which detects the pump discharge pressure.

(17) In addition, as shown in FIGS. 3 and 4, in the embodiment, there are provided a first function setting portion 20a, a second function setting portion 20d and a third function setting portion 20e which are included in the main controller 20. The relation between the operation amount detected by the pressure sensor 18, i.e. a lever operation amount, and a target engine speed are set in the first function setting portion 20a. The relation between the operation speed calculated by the calculation portion 20c and the target engine speed is set in the second function setting portion 20d. The relation between the pump discharge pressure detected by the discharge pressure sensor 19 and the target engine speed is set in the third function setting portion 20e.

(18) In the aforementioned calculation portion 20c, the operation speed of the operating device, i.e. a lever operation speed, is calculated based on a signal which is outputted from the pressure sensor 18 this time and a signal which was outputted from the pressure sensor 18 last time and is stored in a memory 20b of the main controller 20.

(19) As shown in the diagram (a) of FIG. 4, the first function setting portion 20a includes a first operation amount threshold 1 which corresponds to an operation amount regarded as the operating device has been operated, and a second operation amount threshold 2 which is a value larger than the first operation amount threshold 1 and which corresponds to an operation amount of the operating device regarded as having changed from an operation amount for the specific work to an operation amount for the normal work. A target engine speed NF corresponding to a specific work speed is set as a value which is higher than a target engine speed NI corresponding to the idling speed but lower than a target engine speed NG corresponding to the normal work speed.

(20) Incidentally, the first function setting portion 20a may be configured to include a third operation amount threshold 3 which is a value larger than the second operation amount threshold 2 and to have a setting relation in which the target engine speed is increased gradually as the operation amount of the operating device increases from the second operation amount threshold 2 toward the third operation amount threshold 3, as designated by the broken line in the diagram (a) of FIG. 4.

(21) In addition, as shown in the diagram (b) of FIG. 4, the second function setting portion 20d includes an operation speed threshold corresponding to an operation speed of the operating device regarded as having changed from an operation speed for the specific work to an operation speed for the normal work.

(22) In addition, as shown in the diagram (c) of FIG. 4, the third function setting portion 20e includes a first discharge pressure threshold 1 which corresponds to pump discharge pressure regarded as the operating device has been operated from the neutral position, and a second discharge pressure threshold 2 which is a value larger than the first discharge pressure threshold 1 and which corresponds to pump discharge pressure regarded as having changed from discharge pressure for the specific work to discharge pressure for the normal work.

(23) Incidentally, the third threshold setting portion 20e may be configured to include a third discharge pressure threshold 3 which is a value larger than the second discharge pressure threshold 2 and to have a setting relation in which the target engine speed is increased gradually as the pump discharge pressure increases from the second discharge pressure threshold 2 toward the third discharge pressure threshold 3, as designated by the broken line in the diagram (c) of FIG. 4.

(24) In addition, in the embodiment, there are provided a largest value selection portion 20f and an engine controller 21. The largest value selection portion 20f is included in the main controller 20 to select a largest value from the target engine speed outputted from the first function setting portion 20a, the target engine speed outputted from the second function setting portion 20d, and the target engine speed outputted from the third function setting portion 20e. The engine controller 21 controls the speed of the engine 11 in accordance with the largest value of the target engine speed outputted from the largest value selection portion 20f.

(25) In the embodiment configured thus, when the operating device such as the boom operating device 16 is kept at the neutral position, the lever operation amount of the boom operating device 16 is smaller than the first operation amount threshold 1 of the first function setting portion 20a, the lever operation speed of the boom operating device 16 is also smaller than the operation speed threshold of the second function setting portion 20d and the pump discharge pressure of the main pump 12 is also smaller than the first threshold 1 of the third function setting value 20e, with a result that the target engine speed NI corresponding to the idling speed is outputted to the engine controller 21 from the largest value selection portion 20f. Consequently, the engine 11 is driven at the idling speed and kept at a work stop state.

(26) In addition, when, for example, the boom operating device 16 has been operated by a large amount from the neutral position in order to perform the normal work such as soil excavation work, the lever operation amount of the boom operating device 16 becomes larger than the second operation amount threshold 2 of the first function setting portion 20a, the lever operation speed of the boom operating device 16 also becomes larger than the operation speed threshold of the second function setting portion 20d, and the pump discharge pressure of the main pump 12 also becomes larger than the second discharge pressure threshold 2 of the third function setting portion 20e, with a result that the target engine speed NG corresponding to the normal work speed is outputted to the engine controller 21 from the largest value selection portion 20f. Consequently, the engine 11 is driven at the normal work speed, and the main pump 12 is driven by a large driving power to supply discharged pressure oil at a large flow rate to the boom cylinder 7 through the boom directional control valve 14. Thus, desired normal work can be performed.

(27) In addition, when, for example, the boom operating device 16 has been operated by a smaller amount than that for the normal work in order to perform light load work such as soil leveling work, i.e. the specific work, the lever operation amount of the boom operating device 16 is kept between the first operation amount threshold 1 and the second operation amount threshold 2 of the first function setting portion 20a, the lever operation speed of the boom operating device 16 is kept to be smaller than the operation speed threshold of the second function setting portion 20d, and the pump discharge pressure of the main pump 12 is kept between the first discharge pressure threshold 1 and the second discharge pressure threshold 2 of the third function setting portion 20e, with a result that the target engine speed NF corresponding to the specific work speed is outputted to the engine controller 21 from the largest value selection portion 20f. Consequently, the engine 11 is driven at the specific work speed serving as a speed smaller than the normal work speed, and the main pump 12 is driven by a smaller driving power than that for the normal work to supply discharged pressure oil at a smaller flow rate to the boom cylinder 7 through the boom directional control valve 14. Thus, desired specific work can be performed.

(28) According to the embodiment configured thus, during execution of the specific work which is performed with the operation amount of the operating device being made small in the state in which the engine 11 is kept at the idling speed, the main controller 20 keeps the speed of the engine 11 at the specific work speed serving as a speed higher than the idling speed but lower than the normal work speed, as described above. Thus, in the embodiment, the flow rate of pressure oil discharged from the main pump 12 becomes smaller than that for the normal work so that the flow rate of pressure oil discharged from the main pump 12 and returned to a tank through the directional control valve such as the boom directional control valve 16 can be reduced. Therefore, an energy loss can be reduced.

(29) Incidentally, the third operation amount threshold 3 is set in the first function setting portion 20a of the main controller 20 so that the target engine speed can be increased gradually as the lever operation amount increases from the second operation amount threshold 2 to the third operation amount threshold 3, as designated by the broken line in the diagram (a) of FIG. 4. In addition, the third discharge pressure threshold 73 is set in the third function setting portion 20e so that the target engine speed can be increased gradually as the pump discharge pressure increases from the second discharge pressure threshold 2 to the third discharge pressure threshold 3, as designated by the broken line in the diagram (c) of FIG. 4. The configuration made thus can suppress a sudden change in the target engine speed when work is shifted from the specific work which is performed with the operation amount of the operating device being kept small, to the normal work which is performed with the operation amount of the operating device being made large. Consequently, it is possible to suppress the sudden increase of the speed of the engine 11, so that it is possible to shift the work smoothly from the specific work to the normal work while securing stable operability of the hydraulic cylinder such as the boom cylinder 7 etc. driving the work implement such as the boom 4 etc. Thus, it is possible to secure excellent workability.

(30) FIG. 5 is a view showing the configuration of a main part of a main controller provided in another embodiment of the present invention.

(31) Also in the other embodiment of the present invention shown in FIG. 5, there are provided a pressure sensor 18 which detects an operation amount of an equivalent operating device to that in the aforementioned embodiment, a calculation portion 20c which is included in the main controller 20 and which calculates an operation speed of the operating device based on a signal outputted from the pressure sensor 18, and a pressure sensor 19 which detects pump discharge pressure. In the other embodiment, there are particularly provided a first setting portion 20g, a second setting portion 20h, and a third setting portion 20i which are included in the main controller 20. A target engine speed corresponding to a normal work speed is set in the first setting portion 20g. A specific work speed serving as a speed lower than the normal work speed is set in the second setting portion 20h. An idling speed further lower than the specific work speed is set in the third setting portion 20i. In addition, in the other embodiment, there are provided a switching portion 20j and an engine controller 21. The switching portion 20j selects one from the target engine speed set in the first setting portion 20g, the target engine speed set in the second setting portion 20h and the target engine speed set in the third setting portion in accordance with the operation amount of the operating device detected by the pressure sensor 18, the operation speed of the operating device calculated by the calculation portion 20c and the pump discharge pressure detected by the discharge pressure sensor 19, and outputs the selected target engine speed. The engine controller 21 controls the speed of the engine 11 in accordance with the target engine speed outputted from the switching portion 20j. The remaining configuration is equivalent to the aforementioned configuration shown in FIGS. 1 and 2.

(32) FIG. 6 is a flow chart showing a processing procedure in the main controller shown in FIG. 5.

(33) As shown in FIG. 6, in the other embodiment, determination is first made in the main controller 20 as to whether an operating device has been operated or not (step S1). This determination is made based on a signal outputted from the pressure sensor 18. When the determination is No, i.e. when the determination is made that the operating device has not been operated, the switching portion 20j performs a process for outputting an idling speed set in the third setting portion 20i to the engine controller 21 (step S2). Consequently, the engine 11 is driven at the idling speed and kept at a work stop state.

(34) When the determination in the step S1 is Yes, i.e. when the operating device is regarded as having been operated from a neutral position, determination is made as to whether the operation amount of the operating device is at most equal to a predetermined threshold or not (step S3). This threshold corresponds to an operation amount regarded as having changed from an operation amount for specific work such as light load work to an operation amount for normal work such as excavation work. Accordingly, when the determination in the step S3 is No, i.e. when the determination is made that the operating device has been operated largely with the intention of doing the normal work, the switching portion 20j performs a process for outputting a normal work speed set in the first setting portion 20g to the engine controller 21 (step S4). Consequently, the engine 11 is driven at the normal work speed to thereby increase the flow rate of pressure oil discharged from the main pump 12. Thus, the normal work such as excavation work is performed.

(35) When the determination in the step S3 is Yes, i.e. when the determination is made that the lever operation amount of the operating device is at most equal to the predetermined threshold , determination is made as to whether the operation speed of the operating device is at most equal to a predetermined threshold or not (step S5). This threshold corresponds to an operation speed regarded as having changed from an operation speed for the specific work to an operation speed for the normal work. Accordingly, when the determination in the step S5 is No, i.e. when the determination is made that the operation speed of the operating device is larger than the threshold , the switching portion 20j performs a process for outputting the normal work speed set in the first setting portion 20g to the engine controller 21 (step S4). Consequently, the engine 11 is driven at the normal work speed as described above.

(36) When the determination in the step S5 is Yes, i.e. when the operation speed of the operating device is at most equal to the threshold , determination is made as to whether the pump discharge pressure of the main pump 12 is at most equal to a threshold Px or not (step S6). This threshold Px corresponds to pump discharge pressure regarded as having changed from pump discharge pressure for the specific work to pump discharge pressure for the normal work. Accordingly, when the determination in the step S6 is No, i.e. when the determination is made that the pump discharge pressure of the operating device is larger than the threshold Px, the switching portion 20j performs a process for outputting the normal work speed set in the first setting portion 20g to the engine controller 21 (step S4). Consequently, the engine 11 is driven at the normal work speed as described above.

(37) When the determination in the step S6 is Yes, i.e. when the determination is made that the pump discharge pressure of the operating device is at most equal to the threshold Px, the specific work is regarded as being requested to be executed and the switching portion 20j performs a process for outputting the specific work speed set in the second setting portion 20h to the engine controller 21 (step S7). Consequently, the engine 11 is driven at the specific work speed so that the flow rate of pressure oil discharged from the main pump 12 can be suppressed to be smaller than that for the normal work. Thus, light load work such as leveling work, i.e. the specific work is performed. The other embodiment configured thus can obtain an equivalent effect to that of the aforementioned embodiment.

(38) Incidentally, in the aforementioned other embodiment, configuration may be made so that a low pass filter can be provided between the switching portion 20j of the main controller 20 and the engine controller 21.

(39) When the working machine configured thus shifts its work from specific work which is performed with the operation amount of the operating device being kept small, to normal work which is performed with the operation amount of the operating device being made large, a target engine speed outputted from the switching portion 20j can be outputted to the engine controller 21 with a time lag provided by the low pass filter. Consequently, it is possible to suppress the sudden increase of the speed of the engine 11, so that it is possible to shift the work smoothly from the specific work to the normal work while securing stable operability of a hydraulic cylinder such as the boom cylinder 7 driving a work implement such as the boom 4. Thus, it is possible to secure excellent workability.

(40) Incidentally, although execution of the specific work is detected based on three detection factors, i.e. the operation amount of the operating device, the operation speed of the operating device and the pump discharge pressure in each of the embodiment shown in FIGS. 1 to 4 and the other embodiment shown in FIGS. 5 and 6, the present invention is not limited to detection of the execution of the specific work in the aforementioned manner. That is, the execution of the specific work may be detected based on one or two of the operation amount of the operating device, the operation speed of the operating device and the pump discharge pressure.

REFERENCE SIGNS LIST

(41) 3 front working device 4 boom (work implement) 5 arm (work implement) 6 bucket (work implement) 7 boom cylinder (hydraulic cylinder) 8 arm cylinder (hydraulic cylinder) 11 engine 12 main pump 13 pilot pump 14 boom directional control valve 15 arm directional control valve 16 boom operating device 17 arm operating device 18 pressure sensor 19 discharge pressure sensor 20 main controller 20a first function setting portion 20b memory 20c calculation portion 20d second function portion 20e third function portion 20f largest value selection portion 20g first setting portion 20h second setting portion 20i third setting portion 20j switching portion 21 engine controller 1 first operation amount threshold 2 second operation amount threshold 3 third operation amount threshold operation speed threshold 1 first discharge pressure threshold 2 second discharge pressure threshold 3 third discharge pressure threshold